The invention relates to a cutting device for electrotomy.
It has long been known in surgery to use high-frequency AC current in a frequency range from 300 kHz to 2 MHz for the coagulation and separation of tissue, where the treated tissue is coagulated or vaporised; this is designated electro-coagulation or electrotomy. A differentiation must be made between monopolar and bipolar HF thermotherapy.
With monopolar HF thermotherapy, one electrode--also designated the neutral electrode--is designed as a large surface area patient outlet and is disposed near the point of intervention on the patient. The shape of the actual working electrode--also designated the active electrode--is adapted to the respective application. In this way, large surface area ball, plate or needle electrodes are used for tissue coagulation, whilst lancet or loop electrodes are used for the separation of tissue.
On the other hand, with bipolar HF thermotherapy, both electrodes are arranged directly next to the point of intervention so that the effect of the AC current is limited to the direct area of intervention which provides a high degree of safety for the patient and the user, since accidents as a result of capacitative leakage current or burning on the neutral electrode can no longer occur. A further advantage of bipolar HF thermotherapy is the significantly-reduced load resistance of the tissue between the two electrodes which reduces the required generator power whilst maintaining the thermal effect.
Furthermore, HF thermotherapy can be further subdivided according to the position of the electrodes into surface coagulation on the one hand and deep coagulation on the other hand.
With surface coagulation, two touch electrodes disposed in parallel are used with the bipolar technique, these electrodes being placed on the tissue surface, wherein the tissue which lies beneath is heated and coagulated as a result of the flow of current.
With deep coagulation, it is known to use needle, lancet or loop electrodes for monopolar electrotomy. Here, electric light arcs must be generated at the active electrode in order to vaporise tissue which lies in front of the active electrode, hence cutting the tissue. This is relatively easy with the monopolar technique, since this only requires a certain field strength to activate a sparkover at the active electrode. On the other hand, the bipolar technique places greater demand on the conception of the electrode configuration, since the physical processes in this connection are not so simple to control. In consequence, as a result of the necessary miniaturisation of the neutral electrode, bipolar electrode arrangements tend to change the electrode arrangement into different and indifferent electrodes, whereupon the functionality is effected. For this reason, only a few bipolar electrode arrangements are known for deep coagulation, such as, for example, the ball-needle arrangement for laparoscopic electrotomy and the bipolar needle electrode which, amongst others, is suitable for myomotherapy.
This known bipolar electrode arrangement comprises two needle electrodes disposed in parallel which are stuck into the tissue, whereupon the tissue lying between the electrodes is heated as a result of the current flow and is thus coagulated. However, this bipolar electrode arrangement cannot be seen as a cutting apparatus for HF surgery as a result of its dependence on monopolar dissection hooks. Furthermore, a disadvantage with the known bipolar electrode arrangement is the relatively labourious placement of the electrodes with two insertion points. Furthermore, the field distribution can only be relatively inexactly determined by the user, since the relative position of the two electrodes with regard to one another cannot usually be exactly specified.